Siemens SIMATIC S5-100U, System Manual

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S5-100U The Integral Real-Time Clock
12 The Integral Real-Time Clock, for CPU 103
Version 8MA02 and Higher
12.1 Function
The integral real-time clock offers the following possibilities of controlling the process sequence:
• Clock and calendar function
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Used to configure clock-time dependent control, for example
• Prompt and alarm function
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Used to monitor the duration of a process, for example
• Operating hours counter
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Used to monitor inspection intervals, for example
The clock begins running when you supply voltage to the programmable controller. The default is
April 1, 1992, 12:00 o’clock. You set the clock by setting its parameters.
There are two possibilities.
• With CPU 103 version 8MA03, you can set the clock parameters in DB1 (see section 12.2).
• With CPU 103 version 8MA02 and higher, you can set the clock parameters in the system data
area (see section 12.6) and program the clock in the user program (see section 12.7).
The hardware clock requires a clock data area and a status word in order to function. The location
of both the clock data area and the status word must be stored in system data 8 to 10.
Operating Principle of the Clock
Data exchange between the integral real-time clock and the control program always goes through
the clock data area. The clock stores current values for time, date, and operating hours counter in
the clock data area. You can transfer into the clock data area the values for the time, date, prompt
time, and operating hours counter that you want the clock to use.
You can scan the status word to identify setting errors, for example. Or you can change certain
status word bits to deliberately disable or enable transfer or read operations.
Refer to sections 12.4 and 12.5 for additional information about the clock data area and the status
word. These sections are especially important if you want to set clock parameters in the system
data. If you are new to SIMATIC, you may prefer to set clock parameters in DB1.
EWA 4NEB 812 6120-02b
12-1